Messages in this thread | | | Subject | Re: [PATCH v2 1/2] perf evlist: Ensure grouped events with same cpu map | From | "Jin, Yao" <> | Date | Thu, 28 May 2020 09:47:49 +0800 |
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Hi Jiri,
On 5/28/2020 12:28 AM, Jiri Olsa wrote: > On Wed, May 27, 2020 at 09:49:11PM +0800, Jin, Yao wrote: >> Hi Jiri, >> >> On 5/27/2020 6:28 PM, Jiri Olsa wrote: >>> On Wed, May 27, 2020 at 02:31:03PM +0800, Jin, Yao wrote: >>> >>> SNIP >>> >>>>> Thanks >>>>> Jin Yao >>>> >>>> Issue is found! >>>> >>>> It looks we can't set "pos->leader = pos" in either for_each_group_member() >>>> or in for_each_group_evsel() because it may exit the iteration immediately. >>>> >>>> evlist__for_each_entry(evlist, evsel) { >>>> if (evsel->leader == evsel) >>>> continue; >>>> >>>> if (cpu_maps_matched(evsel->leader, evsel)) >>>> continue; >>>> >>>> pr_warning("WARNING: event cpu maps are not fully matched, " >>>> "disable group\n"); >>>> >>>> for_each_group_member(pos, evsel->leader) { >>>> pos->leader = pos; >>>> pos->core.nr_members = 0; >>>> } >>>> >>>> Let me use the example of '{cycles,unc_cbo_cache_lookup.any_i}' again. >>>> >>>> In evlist: >>>> cycles, >>>> unc_cbo_cache_lookup.any_i, >>>> unc_cbo_cache_lookup.any_i, >>>> unc_cbo_cache_lookup.any_i, >>>> unc_cbo_cache_lookup.any_i, >>>> >>>> When we reach the for_each_group_member at first time, evsel is the first >>>> unc_cbo_cache_lookup.any_i and evsel->leader is cycles. pos is same as the >>>> evsel (the first unc_cbo_cache_lookup.any_i). >>>> >>>> Once we execute "pos->leader = pos;", it's actually "evsel->leader = evsel". >>>> So now evsel->leader is changed to the first unc_cbo_cache_lookup.any_i. >>>> >>>> In next iteration, pos is the second unc_cbo_cache_lookup.any_i. pos->leader >>>> is cycles but unfortunately evsel->leader has been changed to the first >>>> unc_cbo_cache_lookup.any_i. So iteration stops immediately. >>> >>> hum, AFAICS the iteration will not break but continue to next evsel and >>> pass the 'continue' for another group member.. what do I miss? >>> >>> jirka >>> >> >> Let me use this example again. >> >> cycles, >> unc_cbo_cache_lookup.any_i, >> unc_cbo_cache_lookup.any_i, >> unc_cbo_cache_lookup.any_i, >> unc_cbo_cache_lookup.any_i, >> >> Yes, once for_each_group_member breaks (due to the issue in 'pos->leader = >> pos'), evlist__for_each_entry will continue to the second >> unc_cbo_cache_lookup.any_i. But now evsel->leader != evsel (evsel->leader is >> "cycles"), so it will go to cpu_maps_matched. >> >> But actually we don't need to go to cpu_maps_matched again. >> >> for_each_group_member(pos, evsel->leader) { >> pos->leader = pos; >> pos->core.nr_members = 0; >> } >> >> If we solve the issue in above code, for_each_group_member doesn't break, >> the leaders of all members in this group will be set to themselves. >> >> if (evsel->leader == evsel) >> continue; > > I see.. the problem is in the for_each_group_member, how about > saving the leader into separate variable, like below > > jirka > > > --- > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c > index f789103d8306..a754cad3f5a0 100644 > --- a/tools/perf/builtin-stat.c > +++ b/tools/perf/builtin-stat.c > @@ -189,6 +189,51 @@ static struct perf_stat_config stat_config = { > .big_num = true, > }; > > +static bool cpus_map_matched(struct evsel *a, struct evsel *b) > +{ > + if (!a->core.cpus && !b->core.cpus) > + return true; > + > + if (!a->core.cpus || !b->core.cpus) > + return false; > + > + if (a->core.cpus->nr != b->core.cpus->nr) > + return false; > + > + for (int i = 0; i < a->core.cpus->nr; i++) { > + if (a->core.cpus->map[i] != b->core.cpus->map[i]) > + return false; > + } > + > + return true; > +} > + > + > +static void evlist__check_cpu_maps(struct evlist *evlist) > +{ > + struct evsel *evsel, *pos, *leader; > + > + evlist__for_each_entry(evlist, evsel) { > + char buf[1024]; > + > + leader = evsel->leader; > + if (leader == evsel) > + continue; > + if (cpus_map_matched(leader, evsel)) > + continue; > + > + evsel__group_desc(leader, buf, sizeof(buf)); > + WARN_ONCE(1, "WARNING: event cpu maps do not match, disabling group:\n"); > + pr_warning(" %s\n", buf); > + > + for_each_group_evsel(pos, leader) { > + pos->leader = pos; > + pos->core.nr_members = 0; > + } > + evsel->leader->core.nr_members = 0; > + } > +} > + > static inline void diff_timespec(struct timespec *r, struct timespec *a, > struct timespec *b) > { > @@ -1956,6 +2001,8 @@ int cmd_stat(int argc, const char **argv) > } else if (argc && !strncmp(argv[0], "rep", 3)) > return __cmd_report(argc, argv); > > + evlist__check_cpu_maps(evsel_list); > + > interval = stat_config.interval; > timeout = stat_config.timeout; > >
This patch looks good. I guess you will post this patch, right? Thanks so much! :)
Thanks Jin Yao
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